1. Field of the Invention
The present invention relates to press-fit terminals for use in circuit boards, etc. and electrical connectors having such a terminal.
2. Description of the Related Art
Japanese UM patent application Kokoku No. 3-14782 discloses such a press-fit terminal.
As shown in FIG. 6, this press-fit terminal comprises a pin-like metallic terminal body 51 and a metallic sleeve 52 provided with a flange. The terminal body 51 has a square cross-section and has a press-fit section tapered toward the tip. The metallic sleeve 52 is put over the press-fit section.
In use, when the press-fit terminal is press-fitted into a through-hole which is provided in a circuit board P and lined with a conductive layer P1, the metallic sleeve 52 engages the circuit board P with the flange, and only the terminal body 51 is press-fitted. As the terminal body 51 is press-fitted, the tapered square press-fit section broadens the metallic sleeve 52 with the edges. Consequently, the terminal body 51 is connected electrically under the contact pressure to the conductive layer P1 of the circuit board P via the metallic sleeve 52.
However, such a conventional press-fit terminal has the following drawbacks:
(1) The metallic sleeve lacks a spring property. The metallic sleeve has a closed annular shape and lacks a spring property so that when the terminal body is press-fitted, satisfactory amounts of expansion are not provided, resulting in the low contact pressure between the metallic sleeve and the conductive layer. PA1 (2) Amounts of expansion of the metallic sleeve tend to be different. The expansion of the metallic sleeve is made by the press-fit of the tapered press-fit section into the metallic sleeve. Consequently, if the length of press-fit (the distance traveled by the terminal body) is constant, manufacturing errors in the radial direction of respective members produce different amounts of sleeve expansion and thus different contact pressures. Consequently, when a plurality of press-fit terminals are press-fitted by the same length of press-fit, there are different contact pressures among the press-fit terminals. If an attempt is made to make the contact pressure constant, then the length of press-fit varies. In addition, since the degree of taper is small, the length of press-fit is large. PA1 (3) A precise finish is required. If an attempt is made to keep the contact pressure within a predetermined range under a constant length of press-fit, high precision work is necessary for the inside diameter of the conductive layer, the inside and outside diameters of the metallic sleeve, and the outside diameter of the press-fit section. PA1 (4) The press-fit terminal is prone to coming out. Since the terminal body is tapered, it tends to come out in the direction. If the degree of taper is reduced to minimize the coming out, then the length of press-fit is too large to be practical.